A conventional golf ball will generally include a flexible solid or wound rubber core enclosed by a relatively hard external cover. The external cover is usually fashioned from Balata or a hard plastic such as SURLYN.TM. and is white or brightly colored to enhance visibility. The outer surface of the external cover has hundreds of dimples that allow the ball to generate lift as it spins and flies through the air, thereby permitting the well struck golf ball to fly great distances.
A typical golf ball has a diameter near or slightly above 1.68 inches. When well struck by a driver or three wood, a typical golf ball can fly a great distance of over 250 yards. Consequently, it can be difficult to find a golf ball that has been struck a great distance when it does not land in the short turf of the fairway. Many golfers, particularly those drawn from the vast multitude of less skilled golfers, would agree that finding a struck golf ball is an important aspect of the game. The difficulty of finding a struck ball increases very rapidly in the fading light of dusk. Obviously, an ordinary golf ball played at dark would be nearly impossible to find even if it does land in the fairway.
Night golf has become more popular in regions of the United States that have intense heat during the summer. Golf course owners and managers have added lighting to their golf courses to extend play into the evening and allow night play. However, it is expensive and difficult to add extensive lighting to a typical golf course that can stretch for over six thousand yards. A ball that performs well and that emits a bright glow of light could benefit golf course owners and managers who wish to offer night golf by allowing them to do so with much less extensive lighting. Aside from increasing the availability of night golf, golfers could also benefit from a light emitting golf ball in fading light conditions such as at dusk. The golfer who wishes to continue play in the fading light of dusk would prefer a golf ball that emits a bright glow of light for high visibility in low light or dark conditions and that is also highly visible during daylight conditions.
Prior art attempts at a golf ball that emits light include a ball covered by U.S. Pat. No. 4,695,055 by Newcomb. U.S. Pat. No. 4,695,055 by Newcomb discloses a translucent plastic ball having a diametrical bore for receiving a corresponding chemi-luminescent light stick. Newcomb's ball has been relatively successful in the market. Although the Newcomb ball glows very brightly, it has a diametric bore and thus is spherically asymmetrical and therefore does not conform to United States Golf Association (U.S.G.A.) rules. The U.S.G.A. Rules of Golf, Appendix III, requires that a golf ball "must not be designed, manufactured or intentionally modified to have properties which differ from those of a spherically symmetrical ball". Newcomb's ball, aside from the inserted light stick, is essentially one piece, solid polymer ball that suffers from significant performance disadvantages of a one piece, solid ball. Further, because the Newcomb ball is translucent, it takes on the color of its surroundings in daylight or twilight conditions. Accordingly, Newcomb's ball, although a useful night ball, is very difficult to find during the daylight or twilight conditions.
Other earlier attempts to introduce phosphorescent materials or layers of phosphorescent materials into a golf ball have met with little success. The phosphorescent materials employed in these previous attempts have typically been zinc sulfide formulations that have been too weak to emit a sufficiently bright and sustained glow of light to make the ball useful at night. The addition of radioactive promethium to such phosphorescent materials can increase brightness but is accompanied by unacceptable health and environmental hazards. Further, earlier glow-in-the-dark golf balls have had translucent, yellowish green covers which make them very difficult to find during the daytime.
What is needed is a golf ball that performs like a ball which conforms to U.S.G.A. rules, that has an outer appearance that is substantially white or brightly colored so that it is easy to see and find during the day, and which has a cover containing a long lasting high luminescence photostorage material so that it can be easily seen at night. Such a ball would be as easy to see and find as a conventional ball in the day or under artificial night lighting and would also be easy to see and find at dusk or at dark.